Method and apparatus for controlling the dispensing of fluid

ABSTRACT

A method is disclosed for controlling the dispensing of fluid from a source at a hydrostatic pressure involving the sequential measuring and dispensing of predetermined volumetric increments of fluid from the source of fluid during different ones of a series of time intervals. Apparatus is also provided for controlling the dispensing of fluid, including metering means for receiving a predetermined increment of fluid and for emptying the predetermined increment of fluid, conduit means for delivering fluid from a source of fluid to the metering means, and control means for actuating the metering means between a condition for receiving one predetermined increment of fluid and a condition for emptying the predetermined increment of fluid.

This is a division of application Ser. No. 732,946, filed Oct. 15, 1976,now U.S. Pat. No. 4,121,584.

BACKGROUND OF THE INVENTION

This invention relates to a method and apparatus for controlling thedispensing of fluid, and more particularly, to a means for controllingthe intravenous administration of a desired dose of fluid into a body.

The present invention is concerned with controlling the dispensing offluid and is primarily concerned with the intravenous administration ofa desired dose of fluid into the body of a patient. In the prior art,apparatus used for the intravenous administration of fluid have beengenerally of two basic varieties. The most common intravenousadministration device is of the gravity flow type in which the rate ofdelivery of fluid is adjusted by means of a variable restriction. Insuch gravity flow systems, the variable restriction is usually providedby a clamping device that deforms a resilient fluid delivery tubeconnected to the hypodermic needle through which the fluid is introducedinto the vascular system of the patient. The gravity flow types ofdevices may vary widely in cost and in the manner and complexity forcontrolling the flow rate of the fluid delivered to the patient.

It has been found that such gravity flow devices employing a variablerestriction are incapable of reliable and uniform operation due to anumber of factors, such as, the tendency of the plastic delivery tube tobe subject to delayed plastic flow under stress, the variations in thehydrostatic pressure from the volume of fluid to be administered,variations in fluid viscosity, and changes in physical position andvascular pressure of the patient that may occur during administration ofa quantity of fluid. In the gravity flow types of devices, theadjustment of the variable restriction governing the flow rate may berequired to be performed manually, which is time consuming and subjectto erroneous adjustment. Also, it is desirable for a doctor or nurse tofrequently check the flow rate in administration of fluid in suchdevices to make sure that it is properly regulated. Moreover, a possibleserious problem may occur in use of these types of devices when acomplete stoppage of flow of fluid takes place, if the device isunattended at the time of exhaustion of the fluid. The unattendedstoppage of flow of fluid at the needle in the patient may result in ablood clot which may cause a dangerous condition for the patient.

The other common variety of intravenous administration device is of thepump type which was designed to overcome various disadvantages of thegravity flow types of intravenous administration devices. Many differentand complicated arrangements have been developed for regulating thepumping action and the quantity of fluid discharged. In the prior art,much design effort has been exerted to overcome the inherent capacity ofthe pump to force air into the patient with possible fatal consequences.The pump type of intravenous administration device has tended to beexpensive, cumbersome, and complicated in structure. Further, thesedevices have been dependent upon a source of power greater than can bereliably and economically supplied by a battery. Various clinicalreasons exist for avoiding the use of alternating current sources ofpower with intravenous administration devices, such as, electro-magneticinterference created by the power supply interfering with sensitiveclinical devices and electrical impulses from the electrical systems forthe pump devices being transmitted through intravenous fluid, which maybe electrically conductive, to patients having sensitive heartconditions.

Accordingly, it is an objective of the present invention to provide anintravenous administration apparatus which is inexpensive and simple tooperate while administering a desired dose of fluid in an accuratelycontrolled manner. In order to accomplish this objective, it isdesirable to provide a method and associated apparatus for intravenousadministration of fluid at an accurately controlled rate irrespective ofvariables, such as, the level of fluid in the source, the venouspressure of the patient, and the viscosity of the fluid. Furthermore, itis desirable to provide an intravenous administration apparatus whichenables automatic and progressive reduction of the rate ofadministration of the fluid at or near the time the desired dose hasbeen administered and before complete exhaustion of the fluid in theadministration apparatus so that air is not injected into the patientand blood clotting at the point of administration is prevented.

It is desirable to provide an intravenous administration apparatus whichis small in size, light in weight, easily portable, and rugged indesign. It is also desirable to provide such apparatus which includes areusable timer capable of a long expectancy of use and a small,portable, replaceable power supply capable of supplying power to theapparatus. It is further highly desirable to provide an intravenousadministration apparatus in which the parts of the apparatus throughwhich the fluid passes is provided by a disposable unit, which isreplaced after each use for easily maintaining the apparatus in asterile condition. Moreover, it is desirable to provide an intravenousadministration apparatus in which the parts of the apparatus are adaptedto cooperate together in operative relationship only when the apparatusis properly assembled and conditioned for safe administration of fluidand provide such an apparatus which minimizes the likelihood of error bythe person responsible for performing the intravenous administration offluid to the patient.

SUMMARY OF THE INVENTION

In accordance with the present invention, a new and improved method andapparatus has been provided with novel features which cooperate toenable an economical, accurately controlled and reliable arrangement forintravenous administration of a volume of fluid. Accordingly, these andother objects are achieved by providing a novel method for controllingthe dispensing of a fluid from a source at a hydrostatic pressure, whichcomprises the procedure of measuring the fluid from the source intopredetermined volumetric increments for dispensing the fluid, providingtime intervals for measuring and dispensing of the predeterminedvolumetric increments of fluid, and then sequentially metering each ofthe predetermined volumetric increments of fluid during different onesof the time intervals. In accordance with the preferred process ofdispensing the fluid, the predetermined volumetric increments arereleased from the source of fluid by providing a receptacle having asize of the predetermined volumetric increment and the receptacle isfilled with fluid by gravity flow from the source of fluid and then thefluid is emptied from the receptacle for administration during each ofthe time intervals.

The preferred apparatus employed in accordance with the presentinvention for controlling the dispensing of fluid at a hydrostaticpressure includes metering means for receiving a predetermined incrementof fluid and for emptying the predetermined increment of fluid. Inaddition, the apparatus has conduit means for delivering fluid to themetering means from a source of fluid having a supply of predeterminedincrements of fluid, and control means for actuating the metering meansbetween a condition for receiving a predetermined increment of fluid anda condition for emptying the predetermined increment of fluid.

The fluid from the source is dispensed through the metering means by themetering means sequentially receiving and emptying each of thepredetermined increments of fluid. For this purpose, the metering meanshas a metering chamber and the apparatus further includes valve meansfor regulating the receiving and emptying of fluid by the meteringchamber. The valve means is preferably provided by an inlet valveconnected with one part of the metering chamber and an outlet valveconnected with another part of the metering chamber, the inlet andoutlet valves being operable in response to actuation from the controlmeans to permit the metering chamber to receive and empty thepredetermined increments of fluid. The control means includes timermeans for sequentially providing a time interval in which the inletvalve permits passage of fluid into the metering chamber and the outletvalve prevents passage of fluid, and the timer means provides anothertime interval in which the inlet valve prevents passage of fluid intothe metering chamber and the outlet valve permits passage of thepredetermined increment of fluid from the metering chamber.

In one form of the invention, the control means or unit includesreleasable fastening means, which may be provided by retaining andpositioning means, cooperating with the metering means or unit to holdthe metering unit in fixed operative relationship with the control unitfor having the valve means responsive to the control unit. Also,preferably, the metering unit includes hydraulic means with a fluidchamber receiving fluid from the metering chamber for having fluid inthe fluid chamber move into the metering chamber to cause air in themetering chamber to be expelled through the conduit means, when theretaining and positioning means moves the metering unit into the fixedoperative relationship. In this arrangement, the control unit includesactuating means cooperable with the hydraulic means to actuate thehydraulic means to move fluid in the fluid chamber into the meteringchamber when the retaining means couples the components together inoperative relationship. In order to assure that air has been expelledfrom the metering chamber when the apparatus is to be operated, thecontrol unit further includes interlock sensor means for sensing fluidin the fluid chamber and preventing the retaining and positioning meansfrom moving the metering unit into the fixed operative relationship withthe control unit, when a predetermined volume of fluid is not present inthe fluid chamber for being moved into the metering chamber to purge airfrom the metering chamber.

In still a further arrangement of the present invention, the apparatusincludes a reservoir chamber adapted to receive a portion of theincrements of fluid from the source of fluid and to hold the fluid at asecond hydrostatic pressure, and inlet means connects the reservoirchamber with the metering chamber. When the source of fluid has beenemptied in this arrangement, the second hydrostatic pressure of thefluid in the reservoir chamber is only sufficient to have the meteringchamber receive a portion of a predetermined increment of fluid from thereservoir chamber in the time interval provided, so that continuedmetering of fluid to the patient is provided at a reduced rate toprevent blood clotting at the hypodermic needle in the patient. In thismanner, a longer time is allowed for the person responsible foradministering the intravenous dose to return to the patient and removethe apparatus at or after the time that the desired dose has beenadministered to the patient.

The arrangement of the metering unit and control unit in accordance withthe present invention is such that, in dispensing the fluid, the fluidpasses through the metering unit without contacting the control unit.Hence, the control unit does not have to be maintained in a sterile oruncontaminated condition. The control unit will be reused and only themetering unit, which is made as a disposable item, will be discardedafter having been used once. Thereafter, upon the next desired use ofthe apparatus, a new metering unit is used in cooperation with thecontrol unit. It should be appreciated that the intravenousadministration apparatus of the present invention can be used for manyintravenous administrations of fluid and only requires replacement ofthe inexpensive metering unit between uses. Further, the features of thepresent invention minimize the likelihood or error in administration offluid by the person responsible for using the apparatus and has manysafety features to prevent the occurrence of dangerous conditions to thepatient during the intravenous administration of the fluid.

For a better understanding of these and other features and advantages ofthe present invention, reference is made to the following drawings, inwhich:

FIG. 1 is an elevational view showing an apparatus for controlling thedispensing of fluid embodying the present invention connected with acontainer of fluid;

FIG. 2 is a perspective view of the control unit and metering unit ofFIG. 1 and showing the units prior to being fastened together;

FIG. 3 is a perspective view of the control unit and metering unit ofFIG. 2 but showing the units fastened together in operativerelationship;

FIG. 4 is an enlarged fragmentary sectional view taken along line 4--4of FIG. 2;

FIG. 5 is a fragmentary side elevational view of the metering unit ofFIG. 4 but showing the cover panel of the metering unit and the meteringunit diaphragm removed;

FIG. 6 is a fragmentary perspective view of the metering unit diaphragmof FIG. 4;

FIG. 7 is a sectional view taken along line 7--7 of FIG. 5;

FIG. 8 is a sectional view taken along line 8--8 of FIG. 1;

FIG. 9 is a fragmentary sectional view taken along line 9--9 of FIG. 8;

FIG. 10 is a sectional view taken along line 10--10 of FIG. 9;

FIG. 11 is a fragmentary sectional view taken along line 11--11 of FIG.9;

FIG. 12 is a fragmentary sectional view taken along line 12--12 of FIG.9;

FIG. 13 is a reduced-dimension perspective view of one of the valveactuator pins of FIG. 9;

FIG. 14 is a sectional view taken along line 14--14 of FIG. 8 andshowing the control unit in the condition in which the metering unit(shown in dot-and-dashed lines) is coupled to the control unit;

FIG. 15 is a sectional view similar to FIG. 14 but showing the retainingand positioning means of the control unit in a condition in which themetering unit (shown in dot-and-dashed lines) is released from, orreceived by, the control unit;

FIG. 16 is a fragmentary sectional view of a portion of the meteringunit and a portion of the control unit and showing the interlock sensormechanism of the control unit in a condition for preventing theretaining and positioning means from moving the metering unit into fixedoperative relationship with the control unit;

FIG. 17 is a fragmentary sectional view of a portion of the meteringunit and a portion of the control unit of FIG. 16 but showing theinterlock sensor mechanism of the control unit in a condition forpermitting the retaining and positioning means to move the metering unitinto fixed operative relationship with the control unit;

FIG. 18 is a fragmentary sectional view of an alternative embodiment ofa metering unit which may be employed in accordance with the presentinvention;

FIG. 19 is a plan view of the metering unit of FIG. 18; and

FIG. 20 is an electrical schematic diagram, partly in block form,illustrating the timer control circuit for providing time intervalsduring which the control unit actuates the metering unit to receive andempty fluid.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The apparatus of the present invention may be used in many differentapplications for controlling the rate of flow of fluid from a source offluid. The use of the present apparatus is not limited to administrationof fluid from a fixed volume or quantity of fluid. The apparatus can beused, for example, in proportioning the mixture of two or moreingredients in a mixing or processing operation where one or moreapparatus in accordance with the present invention is employed. Whilethe apparatus for controlling the dispensing of fluid at a hydrostaticpressure in accordance with the present invention may be used fordispensing fluid in a wide variety of applications, the apparatus willbe described in use in intravenous administration of a volume of fluidas a dose injected in a host, which may be an animal or human and willbe referred to hereinafter as a patient. The apparatus of the presentinvention is particularly useful in this latter application where anaccurately controlled rate of administration of a fluid is required andsafety in operation of the apparatus is important.

Referring now to the embodiment of the invention illustrated in FIG. 1,the invention is shown in use for intravenous administration of fluid toa patient (not shown). The intravenous administration apparatusgenerally designated 10 for controlling the dispensing of fluid at ahydrostatic pressure to a patient is connected to a source of fluid 12,which is shown as a fluid storage bottle or container adapted to besupported above the apparatus 10, which in turn is preferably positioneda distance above the point of application of the fluid into the patient.The fluid may be administered into the patient by a hypodermic needle(not shown) inserted into the vascular system of the patient andconnected to the output of the apparatus 10 by suitable, flexible tubing14. It is preferred for the apparatus 10 to be suspended at a height ofat least thirty inches above the point of application to the patient tocause fluid to flow from the container through the apparatus to thepatient by gravity flow. The hydrostatic pressure of the fluid asreferred to herein indicates the force or pressure that the fluid exertsas it flows into the apparatus 10, and in the application of theapparatus in FIG. 1, the hydrostatic pressure corresponds to the forceor pressure of gravity. Of course, in intravenous administration, theterm fluid is used to indicate a liquid.

There is shown in FIGS. 1-3 the apparatus 10 comprising a metering meansor unit generally designated 16 and a control means or unit generallydesignated 18. The metering unit 16 and control unit 18, which are shownseparated in FIG. 2, are adapted to interfit together, as indicated inFIGS. 1 and 3, with the control unit having releasable fastening meanscooperating with the metering unit for holding the metering unit infixed operative relationship to the control unit 18. The metering unitand control unit are adapted to cooperate together in operativerelationship such that in dispensing the fluid by the apparatus, fluidpasses through the metering unit 16 without contacting the control unit18. More particularly, the metering unit 16 is provided for receivingpredetermined increments of fluid from fluid supply bottle or container12 through inlet tube or conduit means 20 and for emptying thepredetermined increments of fluid through outlet tube or conduit means14 to the patient. Control unit 18 is provided for actuating themetering unit between a condition for receiving a predeterminedincrement of fluid and a condition for emptying the predeterminedincrement of fluid in a sequential manner.

According to the preferred process of use of the invention, the fluidfrom the supply container is measured into predetermined volumetricincrements in the metering unit and time intervals are set for measuringand dispensing of the predetermined volumetric increments of fluidthrough the metering unit. In this procedure, the invention providessequential measuring and dispensing of each of the predeterminedvolumetric increments of fluid during different ones of the timeintervals. The measuring and dispensing of the volumetric increments offluid is referred to herein as metering of fluid. In this arrangement,the metering unit 16 is provided with a receptacle or metering chamberhaving a size of the predetermined volumetric increment and thereceptacle is filled with fluid by gravity flow from the fluid supplycontainer and then the receptacle is emptied of fluid for intravenousadministration into the body during each of the time intervals, as willbe explained more fully hereinafter.

The metering unit 16 for receiving the fluid from the container 12 andemptying the fluid in predetermined volumetric increments to the patientis shown most clearly in FIGS. 4, 5, and 9. Metering unit 16 includes areservoir or drip chamber 22, metering chamber 24, inlet means orconduit 26 connected between drip chamber 22 and metering chamber 24,and outlet means or conduit 28 extending from the metering chamber to anenlarged fluid chamber 30. The fluid from fluid chamber 30 passesthrough outlet passage 32 into tube 14, which is received in anincreased diameter recessed encircling passage 32. The outlet conduit 28also communicates directly with outlet passage 32 by means of a channelor groove 32a formed in body portion 34 and extending through fluidchamber 30, as shown in FIGS. 4, 5, and 9. Metering unit 16 ispreferably made of a rigid plastic material, such as polystyrene, andincludes a main body member or portion 34 and a cover portion or panel36, which divides the metering unit into two parts in forming a portionof inlet conduit 26, metering chamber 24, outlet conduit 28, and fluidchamber 30, as shown most clearly in FIGS. 4 and 9. Further, a resilientmetering diaphragm 38 of resilient plastic material, such aspolyurethane, is captured between the metering unit body portion 34 andthe metering unit cover panel 36. The metering unit body portion 34 andmetering unit cover panel 36 with diaphragm 38 captured therebetween arepreferably joined together by ultrasonic or high-frequency inductionbonding, or may be joined together by any suitable epoxy or bondingcompound or by screws.

As shown most clearly in FIGS. 4, 5, and 9, the inlet conduit 26 hasinlet valve means generally designated 40 therein and is aserpentine-shaped passage around raised portion or projection 42, whichcloses inlet conduit 26 in body portion 34 and forms a valve face.Cavity 44 formed as a recess in cover panel 36 provides a valve cavityand facilitates flow of fluid around projection 42 in inlet conduit 26.Similarly, outlet conduit 28 has outlet valve means generally designated46 therein and is a serpentine-shaped passage around raised portion orprojection 48, which closes outlet conduit 28 in body portion 34 andforms a valve face. Cavity 50 formed as a recess in cover panel 36provides a valve cavity and facilitates flow of fluid around projection48 in outlet conduit 28. In this arrangement, the diaphragm 38, as shownin FIG. 6, has a protrusion 52, which provides a resilient valve elementreceived in valve cavity 44 and a second protrusion 54, which provides aresilient valve element received in valve cavity 50. The resilient valveelements 52 and 54 are normally in the position shown in FIG. 4 whichhave the inlet conduit 26 and outlet conduit 28, respectively, in acondition to permit fluid to flow therethrough. The resilient valveelements 52 and 54 are actuated from positions in which the inlet andoutlet conduits are open and to positions in which the inlet and outletconduits are alternately closed by valve actuator means of the controlunit, as will be explained more fully hereinafter.

The metering chamber 24 of the metering unit 16 is formed by two opposedarcuate-shaped domes or cavities 24a and 24b in body portion 34 andcover panel 36, respectively. There is provided in arcuate-shaped dome24a of metering chamber 24 a series of arcuate-shaped recesses 56communicating with drain passage 58, which in turn communicates withoutlet conduit 28. The recesses 56 and passage 58 are provided tofacilitate complete emptying of fluid from the metering chamber when itis desired to empty the fluid from the metering chamber. In thisarrangement, the diaphragm 38 extends through the metering chamber 24and is provided with an arcuate-shaped dome 60, which generally conformsto the shape of arcuate-shaped dome 24a of the metering chamber in itsnormal condition, as shown in FIGS. 4 and 6. The arcuate-shaped dome 60of the diaphragm provides a movable wall and also conforms to the shapeof arcuate-shaped dome 24b of the metering chamber. The diaphragm wall60 is moved by the force of fluid flowing into the metering chamber tobe adjacent dome surface 24b, when the metering chamber is filled withfluid as shown in FIG. 9. A cylindrical air passage 62 is providedthrough cover panel 36 communicating with dome portion 24b of themetering chamber to permit the movement of air from and into themetering chamber behind movable diaphragm wall 60 as the diaphragm wall60 moves between a position in which the metering chamber is emptied, asshown in FIG. 4, and a position in which the metering chamber is filledwith fluid as shown in FIG. 9.

It will be appreciated that, as the diaphragm wall 60 moves back andforth for fluid to be received and emptied from the metering chamber 24,fluid only contacts one side of the diaphragm wall 60 and the areabetween metering chamber dome 24a and diaphragm wall 60 defines theactive fluid receiving and dispensing portion, generally designated 24cin FIG. 4, of the metering chamber. Although the size of the activefluid portion 24c of the metering chamber 24 varies in size as fluidfills and is emptied from the metering chamber, for convenience indescribing the apparatus and its operation, the active fluid portion 24cof the metering chamber 24 will merely be referred to as the meteringchamber 24 for receiving and emptying fluid. In this arrangement, thediaphragm wall 60 provides movable means in the metering chamber forvarying the size of the metering chamber so that the metering unit isoperable in receiving and draining the increments of fluid without airpassing through the metering chamber.

In the embodiment of the diaphragm 38 illustrated in the drawings, thepressure to move the diaphragm wall 60 from the position shown in FIG. 4to the position shown in FIG. 9 is as little as one half inch or less ofwater head. Therefore, there is always more than adequate hydrostaticpressure to cause movement of the diaphragm wall 60 until the fluidsupply above inlet valve 42 is nearly completely exhausted. It is alsonoted that preferably the diaphragm wall 60 moves between its positionin which the metering chamber is empty and its position in which themetering chamber is filled with fluid without substantial resistance orwithout adding substantial pressure to the hydrostatic pressure of thefluid filling the metering chamber. Accordingly, the diaphragm ispreferably made of a thin resilient material.

Although the volumetric capacity of metering chamber 24 may be made tovary widely depending on the quantity of fluid desired to be deliveredby the apparatus in each volumetric increment and the particularapplication of the apparatus involved, in intravenous administration offluid it is preferable that the metering chamber be less than one cubiccentimeter. Particularly, in intravenous administration of fluids tohumans, it is preferable that the volumetric capacity of the meteringchamber for fluid be on the order of two tenths of a milliliter, whichis received and emptied from the metering chamber as the resilientdiaphragm wall 60 moves back and forth. Hence, the predeterminedvolumetric increment of fluid received and emptied by the metering unitduring each time interval will be two tenths of a milliliter of fluidfor this capacity of the apparatus. In this arrangement of the meteringchamber, it is preferable to have inlet conduit 26 and outlet conduit 28of sufficient internal cross-sectional area to permit a flow of twotenths of a milliliter of water through the conduits in five tenths of asecond at a four inch hydrostatic pressure of the water flowing into themetering unit.

The metering unit diaphragm 38 is also provided with a resilientcup-shaped portion 64 arranged to normally extend into fluid chamber 30,as shown in FIG. 4. The cup-shaped portion 64 of diaphragm 38 is movablefrom its normal position to a position where the cup-shaped portionextends into cylindrical opening 66 through cover panel 36 in responseto fluid filling fluid chamber 30, as when fluid is prevented fromflowing through tube 14 (by a closure, not shown, at the lower end oftube 14) as shown in FIG. 17. For example, fluid is prevented fromflowing through tube 14 when the apparatus is assembled and readied foroperation. The cup-shaped portion 64 of the diaphragm 38 is employedwith the fluid chamber 30 to provide hydraulic means cooperable withactuating means in the control unit to move fluid from the fluid chamberinto the metering chamber to cause air in the metering chamber to beexpelled through the inlet conduit 26. The fluid is forced from thefluid chamber when the metering unit is fastened to the control unit, aswill be explained hereinafter in connection with assembling the meteringunit with the control unit. A rigid plastic disc 68 is preferably bondedto the bottom surface of the cup-shaped portion 64 of diaphragm 38, asshown in FIG. 4, in order to strengthen the bottom surface of thecup-shaped portion 64.

The outlet conduit 28, which communicates between the metering chamber24 and the fluid chamber 30, has an increased dimension portion 28aadjacent the opening to the fluid chamber. The increased dimensionportion 28a, as shown clearly in FIG. 5, provides an air trap to assurethat air in the fluid chamber 30 passes into the outlet conduit andhence through the metering chamber to the drip chamber 22, as fluid isforced from the fluid chamber 30 through the metering chamber, when themetering unit is being coupled into operative relationship with thecontrol unit.

Referring to control unit 18 of FIGS. 1-3, the control unit 18 has anouter case 80 which has removable side panels 82 and 84 secured to thecase as by screws 86. Case 80 of control unit 18 includes a batterycompartment 88, which may contain battery 90 to provide a source ofpower for electrical circuitry in the control unit. Access to thebattery compartment is provided through removable side panel 82. Theopposite side of case 80 houses control compartment 92, which receiveselectro-magnetic valve actuating means or mechanism generally designated94, shown in dot-and-dashed lines in FIG. 1, and the electronic timermeans generally designated 96, which is also shown in dot-and-dashedlines in FIG. 1 as including components on a circuit board fixed toremovable end panel 84.

The control unit 18 has a central receiving portion or receptacle 98 forreceiving the metering unit in interfitting relationship with thecontrol unit. The control unit receptacle 98 is provided by an opening100 in front panel 102 of control unit case 80, opening 100 dividingfront panel 102 into two sections. More particularly, opening 100 infront panel 102 has an increased dimension step portion 104 along itslength adapted to receive increased dimension step portion 34a of thebody portion 34 of metering unit 16 and a step portion 106 serving toclose a portion of the opening 100 adjacent the area where lower end 36aof cover panel 36 of the metering unit is to be received. In thisarrangement, the metering unit will pass through opening 100 in frontpanel 102 of control unit 18 in only one orientation of the meteringunit. The top panel 108 of the control unit 18 has a generally L-shapedopening 110 with the end of one leg communicating with opening 100, andthe bottom panel 112 of control unit 18 has a generally L-shaped opening114 with the end of one leg communicating with opening 100 in the frontpanel. The openings 110 and 114 are in registry to complete the L-shapedcontrol unit receptacle 98 in the control unit case 80. The control unitreceptacle 98 is adapted to receive mating portions of the metering unit16 and provides a cavity of sufficient size to permit the metering unitto be inserted into the control unit along one leg of the L-shapedreceptacle to a first position in the receptacle, as shown in FIG. 15,and moved laterally along the other leg of the L-shaped receptacle intothe control unit to a second position in which the metering unit is inoperative relationship with the control unit as shown in FIGS. 1, 3, 9,and 14, wherein the electromagnetic valve actuating mechanism of thecontrol unit actuates the valve means of the metering unit to controlthe receiving and emptying of fluid by the metering unit.

For the purpose of moving the metering unit laterally in control unitreceptacle 98 from the first position to the second position to be infixed operative relationship with the control unit, the control unit 18is provided with manually releasable fastening means generallydesignated 116, which cooperates with the metering unit for fastening orholding the metering unit to the control unit. The fastening function ispreferably provided by retaining and positioning means or mechanism alsodesignated 116. The retaining and positioning mechanism 116 preferablyincludes a sliding carriage 118 movable between the first position shownin FIG. 15 for receiving and permitting removal of the metering unit andthe second position shown in FIG. 14 for holding the metering unit infixed operative relationship with the control unit. The sliding carriage118 is preferably made from a piece of sheet metal and is formed witharms 120 and 122 on one side extending through openings in interiorpartition or rib 124 of the control case 80, the partition 124 definingthe interior wall of battery compartment 88. Sliding carriage 118 alsohas arms 126 and 128 extending through openings in internal partition orrib 130 of control case 80, partition 130 forming the internal end wallof control compartment 92. The arms 120, 122, 126, and 128 position thesliding carriage and maintain alignment of the carriage as it movesbetween the first position for receiving the metering unit and thesecond position in which the metering unit is retained in the controlunit.

For ease of movement of sliding carriage 118, arm 122 is generallyU-shaped to receive a roller 132, which may be supported by a screw,between the sides of arm 122, and arms 126 and 128 cooperate withrollers 134 and 136, respectively, which may be supported by screws, inpositioning and guiding movement of the sliding carriage. In order toposition the metering unit 16 on sliding carriage 118 for movement withthe carriage, sliding carriage 118 has a U-shaped keeper 137 with legsor projections 138 and 140 adapted to extend on opposite sides of themetering unit 16. Sliding carriage 118 also has legs 142 and 144 whichextend on opposite sides of the metering unit and support the meteringunit in its movement with the sliding carriage between the firstposition to the second position in the control unit receptacle 98.

Sliding carriage 118 of retaining and positioning mechanism 116 is movedbetween its first position for receiving and removal of the meteringunit and its second position for having the metering unit retained infixed operative relationship with the control unit by actuating lever150 and toggle link 152, as shown in FIGS. 8, 14, and 15. Morespecifically, actuating lever 150 on the outside of the back panel 157has a finger grip projection 154 at one end and is connected at itsother end to pivot stud 156 positioned in small slot 158 in back panel157 of control unit case 80. Toggle link 152 on the inside of back panel157 is connected to actuating link 150 by pivot pin 160 extendingthrough arcuate slot 162 in back panel 157, arcuate slot 162 permittingmovement of pivot pin 160 over the desired movement of actuating lever150. The other end of toggle link 152 is pivotally connected to slidingcarriage 118 by pivot pin 164. Toggle link 152 has an extended endportion 152a with a groove (not shown) adapted to receive one end ofleaf spring 166, which has its other end positioned in a groove inflange 168 of sliding carriage 118. Leaf spring 166 is adapted to biastoggle link 152 in an overcenter position of movement. Stress reliefspring 170, which is held at its opposite ends by tab 172 on back panel157 and pivot stud 156 in conjunction with biasing tab 174 formed inback panel 157, acts to bias pivot stud 156 toward the sliding carriagein slot 158 to relieve stress and provide greater tolerance in movementof the toggle retaining mechanism in cooperating with sliding carriage118.

In operation of retaining mechanism 116, the metering unit is positionedwithin the control unit receptacle 98 with the retaining mechanism inthe position shown in FIG. 15. After the metering unit is moved intocontrol unit receptacle 98 abutting the sliding carriage assembly 118,actuating lever 150 is pivoted from the position shown in FIG. 15clockwise to the position shown in FIG. 14, thereby moving slidingcarriage 118 and the metering unit (shown in dot-and-dashed lines inFIGS. 14 and 15) to the position shown in FIG. 14, wherein the meteringunit 16 is in fixed operative relationship with the control unit 18. Itshould be appreciated that the surfaces of the control unit forming thereceptacle together with the legs of the sliding carriage providealignment means for receiving the metering unit and the metering unitsurfaces provide mating guides for aligning and positioning the meteringunit correctly within the control unit.

As the retaining and positioning mechanism 116 moves the metering unitfrom the first position in FIG. 15 to the second position in controlunit receptacle 98 shown in FIG. 14 for having the metering unit inoperative relationship with the control unit, the hydraulic means,comprising cup-shaped diaphragm element 64 in fluid chamber 30 ofmetering unit 16, is actuated by actuating means, which is provided byram surface 180a of hydraulic actuator boss 180 on partition 130 ofcontrol unit case 80, as shown in FIG. 9. If fluid chamber 30 of thehydraulic means is filled with fluid when the retaining and positioningmechanism moves the metering unit into fixed operative relationship withthe control unit, the fluid in the fluid chamber is forced upwardly intothe metering chamber by the action of ram surface 180a acting on thecup-shaped diaphragm portion 64, as shown in FIG. 17, to move diaphragmportion 64 to a position as shown in FIG. 9. This movement of fluid fromthe fluid chamber into the metering chamber forces air in the meteringchamber to be expelled to the drip chamber 22 in the metering unit 16,which prepares the metering unit for safe operation with the controlunit. In order to sense whether sufficient fluid is in the fluid chamber30 to adequately purge air from the metering chamber 24, interlocksensor means generally designatd 184, as shown most clearly in FIGS.16-17, is provided for sensing fluid in the fluid chamber. The interlocksensor means prevents the sliding carriage 118 of the retaining andpositioning mechanism 116 from moving the metering unit into the fixedoperative relationship when a sufficient volume of fluid is not presentin the fluid chamber 30.

The interlock sensor means or mechanism 184 is provided by plunger 186positioned in a central axial bore through hydraulic actuator boss 180and extending through a reduced diameter opening in partition 130 of thecontrol unit casing 80. Interlock sensor means 184 also includesL-shaped link 188 pivotally attached to back panel 157 of case 80 bypivot pin 190, and connecting rod 192 fixed to the plunger and pivotallyattached to one end of pivoted link 188, as shown in FIGS. 16 and 17.Pivoted link 188 at its other end has a latch member or pawl 194 adaptedto be received in detent 196 in arm 128 of sliding carriage 118. Pivotedlink 188 is normally biased into a position to have pawl 194 engagedetent 196 by helical spring 198, which surrounds a reduced diameterportion 186a of the plunger 186 and acts between the head of plunger 186and partition 130 of the control unit case. In this arrangement, whenthe sliding carriage with the metering unit is moved from its firstposition to its second position, if sufficient fluid is present in thefluid chamber 30 to have the cup-shaped diaphragm portion 64 in opening66 in cover panel 36 of the metering unit, as shown in FIG. 17, theplunger 186 is forced into boss 180 to move pawl 194 of link 188 to aposition where detent 196 on sliding carriage 118 is not engaged by pawl194. However, if sufficient fluid is not present in fluid chamber 30, asshown in FIG. 16, spring 198 acting on plunger 186 will cause thepivoted link 188 to be biased through rod 192 to have pawl 194 engagedetent 196 to prevent sliding carriage 118 from moving the metering unitto its operative position within receptacle 98 of the control unit.

When the retaining and positioning mechanism 116 including slidingcarriage 118 moves the metering unit 16 into control unit receptacle 98to the position shown in FIG. 14, metering unit 16 is in fixed operativerelationship with control unit 18 to have the valve actuator means 94 ofthe control unit operate the valve means 40 and 46 in the metering unit.With the metering unit fastened to the control unit, as represented inFIG. 9, the metering unit would abut against projections 200 ofpartition 130 to space the metering unit a slight distance frompartition 130 to permit air to enter opening 62 into the meteringchamber 24 enabling flexible diaphragm wall 60 to move back and forth inthe metering chamber without substantial air resistance or creating avacuum. Preferably, projections 200 formed on partition 130 of thecontrol unit case 80 are provided by three projections spaced in atriangular manner to accurately position the metering unit adjacentpartition 130 in the control unit. In addition, partition 130 isprovided with two outwardly extending positioning bosses 202 and 204,which are received in mating recesses 206 and 208, respectively, of themetering unit, the bosses 202 and 204 and mating recesses 206 and 208providing positioning and guide means for further aligning the meteringunit in operative relationship with the control unit.

The electro-magnetic valve actuator mechanism 94 of the control unitcomprises two electro-magnetic coil assemblies 210 and 212 wound aroundcore member 214 and spaced apart along the core by support bracket 216,which has a recess 216a in one side adapted to receive a reduceddiameter portion 214a of core 214 between the coil assemblies 210 and212, as shown in FIGS. 9 and 11. The other side of support bracket 216is supported in elongated slot 226 in partition 130. Coil assemblies 210and 212 and core member 214 are further supported by brackets 218 and220, which encircle core member 214 at opposite ends thereof to capturethe coil assemblies therebetween. The brackets 218 and 220 are fixed topartition or wall 130 as by screws 222 and 224, respectively.

The magnetic circuit for the coil assemblies 210 and 212 is completed byrocker armature 230, which has leg 230a bent to extend closely adjacentend 214a of core member 214 and leg 230b bent closely adjacent end 214bof the core member. Rocker armature 230 extends through a recess 216b ofsupport member 216 and is pivotally positioned at beveled surface 216cof support member 216 by leaf spring 232, which has one end fixed in aslot in partition 130 and its other end received in a slot in rockerarmature 230 adjacent the beveled pivot surface 216c. A leaf spring 234is provided to bias rocker armature 230 in an overcenter condition inits two extreme positions about pivot surface 216c, and leaf spring 234is held at one end by pin 236 fixed to end 230b of rocker armature 230and at its other end supported in a recess in bracket 220. By thisarrangement, leaf spring 234 biases rocker armature 230 in theovercenter position in which leg 230a is adjacent end 214a of coremember 214 or in the position in which rocker armature leg 230b ispositioned adjacent end 214b of core member 214.

As rocker armature 230 moves from one extreme of its travel, such aswhen coil 210 is energized pulling rocker armature leg 230a adjacent thecore end 214a shown in FIG. 9, to the other extreme of its travel, suchas when coil assembly 212 is energized pulling rocker armature leg 230badjacent the core end 214b, the rocker armature moves first valveactuator pin 240 and second valve actuator pin 242 between conditionsfor actuating the valve elements 52 and 54, respectively, of the firstand second valve means 40 and 46, respectively, of the metering unit.More specifically, valve actuator pins 240 and 242 extend throughopenings 244 and 246, respectively, in partition 130, the openings 244and 246 extending through bosses 202 and 204, respectively. The valveactuator pins 240 and 242 further extend through openings in the coverpanel 36 of the metering unit into the valve chambers of cavities 44 and46, respectively, to be engagable with the diaphragm valve elements 52and 54, respectively. The outer ends 240a and 242a of the valve actuatorpins 240 and 242, respectively, have beveled surfaces to providewedge-shaped ends to interact with the diaphragm valve elements 52 and54, respectively, in alternately closing inlet conduit 26 and outletconduit 28, respectively. It should be apparent that diaphragm 38provides a seal between the body portion 34 and cover panel 36 of themetering unit so that fluid flowing through the metering unit isprevented from contacting cover panel 36, the valve actuator pins andother structure of the control unit.

The valve actuator pins 240 and 242 are actuated through their couplingto rocker armature 230, as shown most clearly in FIG. 9. Morespecifically, each of valve actuator pins 240 and 242 extend throughrocker armature 230 and have two positioning pins 240b and 240c and 242band 242c, respectively, extending through and axially spaced along thevalve actuator pins on opposite sides of the rocker armature. Biasingsprings 250 and 252 encircle valve pins 240 and 242, respectively, andhave one end fixed to rocker armature 230 and their other ends abuttingwashers 254 and 256, respectively, which encircle the valve pins andrest against positioning pins 240c and 242c, respectively. The valveactuator pins 240 and 242 extend through openings in legs 218a and 220aof brackets 218 and 220, respectively. Guide pins 258 and 260 are fixedto bracket legs 218a and 220a and are received in axial alignment slotsat the ends of valve actuator pins 240 and 242, respectively, such asalignment slot 240d of pin 240 shown in FIG. 13. The guide pins 258 and260 maintain the alignment of the valve actuator pins 240 and 242 as thevalve actuator pins move back and forth in actuating their associatedvalve elements.

With the metering unit 16 in operational position within the controlunit 18, the coil assembly 210 may be energized to have rocker armatureleg 230a drawn to the position shown in FIG. 9 adjacent core end 214a.The magnetic circuit for core assembly 210 in this instance is throughcore member 214, rocker armature leg 230a, and support bracket 216 tothe other side of coil assembly 210. In the condition with coil 210energized, rocker armature 230 will bias valve actuator pin 242 againstdiaphragm valve element 54 to close the outlet valve 46 and prevent flowof fluid through outlet conduit 28. With the inlet valve 42 open and theoutlet valve 46 closed, an increment of fluid is permitted to flow intometering chamber 24 filling the metering chamber, diaphragm wall 60being moved to the position in FIG. 9 with the metering chamber at fullcapacity.

When coil assembly 210 is deenergized and coil assembly 212 isenergized, rocker armature end 230b will be drawn adjacent core end 214bto move valve actuator pin 240 to deform valve element 52, closing inletvalve 42 and hence inlet conduit 26. In this condition, valve actuatorpin 242 does not deform diaphragm valve element 54 and flow of fluid ispermitted through outlet valve 46 and hence outlet conduit 28. With theinlet valve 42 closed and the outlet valve 46 open, the increment offluid in the metering chamber 24 will be emptied and the diaphragm wall60 will collapse the metering chamber to be in its normal position asshown in FIG. 4. Thus, the resilient diaphragm wall 60 provides amovable wall in the metering chamber for varying the size of themetering chamber in response to fluid being received in the meteringchamber and emptied from the metering chamber. This cycle of operationof the inlet and outlet valves is repeated as the coil assemblies 210and 212 are sequentially energized to move rocker armature 230 betweenits extreme positions actuating valve pins 240 and 242 to alternatelyclose the inlet and outlet valves. It should be appreciated that, whenthe metering unit 16 is moved into operative relationship with thecontrol unit 18 by retaining and positioning mechanism 116, one of thevalve actuator pins will be actuating its associated diaphragm valveelement, such as valve actuator pin 242 actuating diaphragm valveelement 54 to close the outlet valve 46 in FIG. 9. The particular valveactuator pin actuated to close its associated valve will depend upon theovercenter position of rocker armature 230 when the units are assembledtogether.

With the metering unit 16 and control unit 18 assembled together inoperative position, it is desirable to be able to permit fluid to flowthrough the metering unit before the coil assemblies 210 and 212 arealternately energized. For this purpose, valve-release cam mechanismgenerally designated 270 is provided to move the engaged valve actuatorpin from closing its associated valve element in the metering unit. Morespecifically, valve-release cam mechanism 270 comprises a slidable cambar 272, as shown in FIG. 12, received in a cavity or recess 274 inpartition 130 of control unit case 80. The cavity 274 is formed in ashape to permit limited longitudinal movement of the cam bar 272. Thecam bar 272 may be held within cavity 274 by any suitable means, such asscrews 276 and 278 having their heads extend over the cam bar in cavity274. Cam bar 272 has tabs 272a and 272b which provide cams adapted tocontact pins 240c and 242c, respectively, if the associated valveactuator pin 240 or 242, respectively, is in a position to close itsassociated valve.

Actuation of cam bar 272 is provided by manual depression of plunger280, which is fixed at one end to flange 272c of the cam bar and at itsother end extends through an opening in top casing panel 108 to receivepush button 282. A helical spring 284 encircles the push button 282between the head of the push button and top panel 108 to bias the pushbutton and, hence, cam bar 272 to one extreme position of its travel inwhich cam bar 272 engages end 274a of cavity 274. When it is desired toopen both valves in the metering unit to permit flow of fluid throughthe metering unit, push button 280 is manually depressed moving cam bar272 along its path of travel to have the appropriate cam tab engage thepositioning pin of the actuated valve actuator pin. For example, in thearrangement shown in FIG. 9, when push button 282 is manually depressedmoving cam bar 272 along its path of travel, cam tab 272b would engagepositioning pin 242b to move valve actuator pin 242 out of deformingengagement with diaphragm valve element 54. A similar movement of valveactuator pin 240 would occur, if valve actuator pin 240 was deformingits diaphragm valve element as when rocker armature 230 is in its otherextreme position of movement.

A circuit for energizing the coil assemblies 210 and 212 isschematically shown, partly in block form, in FIG. 20. The schematicdiaphragm of FIG. 20 illustrates the timer means for sequentiallyproviding a first time interval in which the inlet valve permits passageof fluid into the metering chamber for filling the metering chamber andthe outlet valve is responsive to the valve actuator pin 242 of thecontrol unit to prevent the passage of fluid and providing a second timeinterval in which the inlet valve is responsive to valve actuator pin240 of the control unit to prevent passage of fluid into the meteringchamber and the outlet valve permits emptying of the increment of fluidcontained in the metering chamber. The first time interval and secondtime interval are added to provide a total time interval for a cycle ofoperation of the metering unit with the control unit.

In the schematic diagram of FIG. 20, battery 90, which is located incontrol unit battery compartment 88 as previously mentioned, has itsnegative terminal connected to electrical ground and its positiveterminal connected to manual control switch generally designated 301having pole or switch actuator 302, which is shown as a switch button onfront panel 102 of control unit casing 80 in FIGS. 1-3. The other sideof switch 301 is electrically connected to coils 210 and 212 from commonelectrical line 303, as shown in FIG. 20. The other sides of coils 210and 212 are connected to first timer output circuit 304 and second timeroutput circuit 306, respectively. The first timer output circuit 304 andsecond timer output circuit 306 have switching circuit 308 connectedtherebetween and each of circuits 304, 306, and 308 are electricallyconnected to switch 301 by their connection to common electrical line303 in FIG. 20. The function of first timer output circuit 304, secondtimer output circuit 306, and switching circuit 308 in timer circuit 300is merely to provide the first time interval in which coil 210 isenergized and the second time interval in which coil 212 is energized.Of course, when coil 210 is energized, coil 212 is deenergized, and viceversa. Thereafter, the cycle repeats itself with coil 210 first beingenergized and then deenergized and subsequently coil 212 being energizedand deenergized during the different time intervals. The sum of thenumber of total time intervals would comprise a time period in which adesired dose or quantity of fluid would be administered to the patient.

Circuits of the type of function as set forth above to alternatelyenergize and deenergize coils 210 and 212 are conventional in electricalcircuitry and the design of this type of circuit is within the skill inthe art. The schematic timer circuit 300 of FIG. 20 is merely providedto indicate one type of schematic illustration for a circuit to energizecoils 210 and 212. For example, in one specific arrangement of the timercircuit for FIG. 20, first timer output circuit 304 and second timeroutput circuit 306 are provided by similar electrical components. Firsttimer output circuit 304 is provided by a circuit including aprogrammable unijunction transistor which is rendered conductive by thecharging of a capacitor and controls a circuit through the coil 210, thecharging time of the capacitor being regulated by a variable resistor inthe programmable unijunction transistor circuit. When the capacitor ischarged to a predetermined potential the unijunction transistor isrendered conductive to cause a circuit to be completed through the coil210, and, when the charge on the capacitor is dissipated, theunijunction transistor ceases to conduct and the circuit through coil210 is opened to deenergize the coil 210. Such operation of theprogrammable unijunction transistor circuit also provides an output toswitching circuit 308. A similar type of programmable unijunctiontransistor circuit with a variable resistor and capacitor arrangement togovern the conduction of the programmable unijunction transistor isprovided for second timer output circuit 306 to control the energizingand deenergizing of coil 212 and provide an output to switching circuit308.

With this type of programmable unijunction transistor circuit for thefirst and second timer output circuits, the switching circuit 308 isprovided by a bistable flip-flop circuit, which provides alternatingactivation of the first and second timer output circuits 304 and 306. Anoverall manner of operation for the first and second timer outputcircuits in conjunction with the flip-flop circuit 308 with thecomponents as outlined above would be as follows. When switch 301 isclosed, switching circuit 308 will be in one of its stable conditions tohave one of the timer output circuits begin its cycle of causingenergization of its associated coil. For example, if switching circuit308 is in the condition to have the first timer output circuit 304 beginin its cycle of operation, a capacitor is charged to a potential forrendering conductive its associated programmable unijunction transistorto cause completion of the circuit through the coil 210, therebyenergizing the coil. When the first timer output circuit becomesnon-conductive, current flow through coil 210 will stop. A lightemitting diode 310 is shown connected across coil 210 and is operated bythe voltage created by the collapsing field in coil 210 to energize thelight emitting diode 310. Thus, without draining energy from thebattery, diode 310 provides a light signal indicating that the controlunit is operating. The light emitting diode 310 may be positioned in thefront panel of the control unit casing 80, as shown in FIGS. 1-3, toprovide a clearly visible indication of the operation of the controlunit. When first timer output circuit 304 is actuated between itsconductive and non-conductive states, a signal is provided to flip-flopcircuit 308, which switches it to permit second timer output circuit 306to operate through its cycle of conductive and non-conductive states toenergize coil 212 and reset the flip-flop circuit to begin the cycle ofconduction and non-conduction for the first timer output circuit. Thiscycle of operation continues throughout the administration of a desireddose of fluid, thereby causing the metering chamber to receive and drainthe volumetric increments of fluid of a quantity predetermined by thecapacity of the metering chamber 24.

In the administration of fluid to a patient, it is preferable to havethe time interval for permitting the metering chamber to be drained oremptied longer than the time interval for filling the metering chamber,so that sufficient time will always be allowed to permit completedraining of the metering chamber during each drain cycle or intervalirrespective of the several variables which affect the rate of flow offluid from the metering chamber. The time intervals for operation of theinlet and outlet valves may be set at different lengths by adjusting thevariable resistors which regulate the charging of the capacitors in thefirst and second timer output circuits 304 and 306. In the preferredarrangement of the apparatus, the time interval for the inlet valvebeing open for filling the metering unit would remain constant and neednot be varied in use of the apparatus in controlling the intravenousadministration of fluids. In order to facilitate variations in time forthe outlet valve to be opened, a control dial 312 for controlling theresistance of the variable resistor in the first timer output circuit304 is provided. In this manner, the time for energizing coil 210 and,hence, closing the outlet valve is varied. The dial 312 varying the timeinterval of operation of the first timer output circuit 306 is providedon front panel 102 of control unit case 80, as shown in FIGS. 1-3, andis calibrated in milliliters per minute for ease of use of theapparatus. For example, dial 312 may be calibrated from two tenthsmilliliters per minute of administration of fluid to ten milliliters perminute of administration of fluid to provide a gradation in rate ofadministration of fluid by the apparatus. For each administration of adose of fluid to a patient, dial 312 would be set to a desired flow rateof the fluid.

In the setup of the apparatus in accordance with the present inventionto administer a prescribed dose of fluid to a patient, the metering unit16 is connected to tube 14. A cap (not shown) normally provides closureof the other end of outlet tube 14 and is subsequently removed forconnection of the hypodermic needle to tube 14. Conduit means 20 of themetering unit 16 is plugged into standard dose container or bottle 12,containing the prescribed dose of fluid to be administered. Container 12is then suspended in an inverted position with the metering unitconnected thereto above the level of the patient to whom the dose is tobe administered so that fluid will drain through the metering unit bygravity flow and so that the metering chamber is permitted to draincompletely during each drain interval. For a patient confined to bed,the metering unit should be positioned at a level about thirty inches ormore above the patient. This arrangement provides a sufficient pressuredifferential between the level of fluid in the metering chamber and thevenous pressure of the patient to overcome the venous back pressure ofthe patient and allow complete emptying of the metering chamber duringeach drain interval. Also, the pressure of the fluid flowing from thecontainer by gravity flow provides the fluid at a hydrostatic pressureto properly operate the filling of the metering chamber.

In this orientation of the fluid container 12 and metering unit 16,fluid will flow by gravity down into the metering unit, which willsubsequently be coupled to the control unit, through the inlet valve topartially fill the metering chamber by moving diaphragm wall 60 underthe pressure of the fluid. The fluid will also pass from the meteringchamber through the outlet valve into the fluid chamber, thereby movingcupshaped dome 64 of the diaphragm under the pressure of the fluid toincrease the capacity of fluid chamber 30, as when cup-shaped diaphragmportion 64 is in the position shown in FIG. 17. The fluid in passingthrough the metering unit 16, as described above, will also generallyflow a distance into the top of outlet tube 14 before the pressure ofair will restrain the fluid flow. It should be appreciated that thefluid flowing through the metering unit as described will drip throughthe reservoir or drip chamber 22 without filling the drip chamber orcausing a reservoir of fluid in the drip chamber due to the air capturedtherein.

The control unit 18 is next coupled to the metering unit by insertingthe metering unit into control unit receptacle 98 within the legs ofsliding carriage 118, as when the retaining and positioning mechanism116 of the control unit 18 is in the position shown in FIG. 15 with themetering unit being indicated in dot-and-dashed lines. As previouslymentioned, the surfaces defining the control unit receptacle and themetering unit are provided such that the metering unit fits within thecontrol unit receptacle 98 in only one orientation. The actuating lever150 of the fastening or retaining mechanism 116 is moved in a clockwisedirection, as shown in FIG. 15, to move the sliding carriage and, hence,the metering unit into operative relationship with the control unit, inwhich condition the metering unit is adjacent partition 130 of thecontrol unit so that valve actuator pins 240 and 242 may open and closethe inlet and outlet valves of the metering unit when theelectro-magnetic mechanism 94 is energized. It should be appreciatedthat, with fluid in the fluid chamber, cup-shaped diaphragm portion 64actuates the plunger 186 of interlock sensor means 148 to permit detent196 of sliding carriage 118 to move free of pawl 194 to the secondposition of the sliding carriage shown in FIG. 14.

As the metering unit 16 is moved into fixed operative relationship withthe control unit, the hydraulic actuator moves cup-shaped diaphragmportion 64 into its normal position, thereby forcing fluid from thefluid chamber 30 into metering chamber 24 and drip chamber 22. Thisforcing of fluid from the fluid chamber into the metering chamber purgesair from the metering chamber and communicating conduits and partiallyfills the reservoir or drip chamber 22 with fluid. To purge air from theoutlet tube 14, the cap (not shown) on the tube 14 is removed and valverelease cam mechanism 270 is actuated by briefly depressing push button282 to cause both the inlet and outlet valves to be opened to permitfluid to flow through the metering unit and tube 14. With tube 14 filledwith fluid, the hypodermic needle is connected to the tube in aconventional manner, the hypodermic needle being inserted into thevascular system of the patient.

The apparatus is set to a desired flow rate of the fluid by rotatingdial 312 to the desired point as indicated on the calibration scale onthe front panel. The setting of dial 312 is translated into a desiredrate of administration of each volumetric increment of fluid held by themetering chamber by varying the time interval that the outlet valveremains open for emptying of the predetermined increment of fluid fromthe metering chamber. Initiation of the administration of fluid is begunby actuating switch button 302 to its "ON" position, moving the switchpole 302 to close switch 301 in timer circuit 300. The operation oftimer circuit 300 recycles the electro-magnetic valve actuatingmechanism to cause the filling and emptying of the metering chamber onceduring each cycle of operation of opening and closing the inlet andoutlet valves of the metering unit. As previously mentioned, during eachcycle of operation of the timer circuit, the inlet valve would be opento permit filling of the metering chamber to capacity with diaphragmwall 60 abutting metering chamber surface 24b and then the inlet valvewould be closed and the outlet valve open so that fluid flows by gravityfrom the metering chamber to the patient emptying the metering chamberbefore another cycle of operation. Hence, the inlet valve and outletvalve are alternately opened and closed during each time interval, asrocker armature 230 moves from one of its extreme positions to theother. However, it should be appreciated that when rocker armature 230passes through its neutral position, both the inlet valve and outletvalve are closed by the valve actuator pins 240 and 242, respectively,so that at no time are both valves open when the metering unit isfastened in operative relationship with the control unit.

Normally, the termination of administration of a dose is accomplished bythe removal of the hypodermic needle from the patient immediately uponcompletion of administration of the prescribed volume of fluid and whilefluid is still flowing through the hypodermic needle or immediatelyafter flow of fluid is stopped. The container containing the prescribeddose usually contains a quantity of fluid beyond the prescribed dose forsafety in preventing the stoppage of flow of fluid immediately upon aprescribed dose being administered.

In accordance with the present invention, as hydrostatic pressure in thesupply source container decreases due to the level of fluid beinglowered some distance below the level where the prescribed dose has beenadministered (or the fluid source container has been drained below apredetermined level), the volume of fluid in each increment passingthrough the metering chamber will automatically be gradually reduced.For example, when fluid only remains in the reservoir or drip chamber22, which has the fluid at a lower or second hydrostatic pressure thanthat provided by the fluid in supply container 12, fluid will only fillthe metering chamber to a reduced volume during the time intervals whenthe outlet valve is closed and the inlet valve is open in the meteringunit because the pressure of the fluid is not sufficient to cause fluidto flow into the metering chamber fast enough to fill the meteringchamber to capacity within the time interval provided.

It will also be appreciated that the fluid level at which the reductionin the size of the volumetric increments of fluid in the meteringchamber occurs after the desired dose has been administered will beaffected by the viscosity of the fluid being administered. Nevertheless,the apparatus will operate at a reduced rate of fluid administration toprotect the patient and permit a longer time period for the hypodermicneedle to be removed from the patient by the doctor or nurse withoutserious adverse consequences to the patient. It will further beappreciated that, even after there is insufficient fluid above the inletvalve to cause movement of the diaphragm wall in the metering chamber,air will not pass through the metering chamber due to an inherenttendency of the diaphragm wall 60 to act as a shutoff valve when thehydrostatic pressure in the part of the drainage system directly belowthe metering chamber is below atmospheric pressure.

It should be understood that many modifications may be made in thearrangement of the apparatus in accordance with the present inventionwhile still employing the concept of the invention. A modifiedembodiment of the metering unit is shown, for example, in FIGS. 18 and19. In the embodiment shown in FIGS. 18 and 19, the metering unit hasbeen modified to provide greater effectiveness of the automatic slowingdown of the rate of administration of fluid through the metering unitafter a prescribed dose has been administered. The primary difference instructure of the metering unit of FIGS. 18 and 19 and that of FIGS. 1-4lies in the change in size and location of the reservoir or dripchamber. Metering unit 400 in FIGS. 18 and 19 has a metering unit body402 which is identical to the metering unit body of the metering unit ofFIG. 4 in the provision of the inlet valve, metering chamber, outletvalve, and fluid chamber arrangements. The metering unit 400 has itsreservoir or drip chamber 404 offset, lowered, and enlarged from thelocation in FIG. 4. Drip chamber 404 is enlarged for increased capacityto provide a greater reservoir supply for fluid, and the drip chamber isoffset and lowered with respect to the inlet valve in the meteringchamber in order for the drip chamber to supply the last few cubiccentimeters of fluid to the metering chamber at a very low hydrostaticpressure as the fluid drains from the drip chamber into inlet conduit408. Inlet conduit 408 is shaped to have the fluid flow upwardly along avertical path before proceeding downwardly through the metering unitinlet valve generally designated 110 to the metering chamber. Also, inFIG. 18, the length of inlet passage 406 is increased in order toprovide a sufficient hydrostatic pressure above the metering chamber forreliable operation with a very short time interval for filling themetering chamber. In this arrangement, the rate of administration offluid through the metering unit will decrease significantly before thefluid level in passage 406 is exhausted and will decrease to a minutefraction of the selected rate of administration before stoppingcompletely. In use of the metering unit of FIGS. 18 and 19, thereceptacle of the control unit, such as shown in FIG. 3, would have tobe enlarged and modified in order to accommodate the enlarged and offsetdrip chamber portion of the modified metering unit as would be obviousto those skilled in the art. It should also be understood that the dripchamber illustrated in FIG. 18 could be considered a lower extension ofthe supply container for the purpose of accomplishing the automaticreduction in rate of fluid administration of this invention and thereservoir or drip chamber need not be integrally attached to the body ofthe metering unit as part of the metering unit. For example, thereservoir chamber might be connected to the metering unit by a flexibletube.

It should be appreciated that provision may be made in the apparatus formeans to vary the size of the metering chamber, depending on the desiredquantity of fluid to be delivered in each increment received anddispensed by the metering chamber. An adjustable member could beprovided from the control unit extending through opening 62 of themetering unit into the metering chamber to vary the stroke of thediaphragm wall 60 in filling the metering chamber with the desiredincrement of fluid. Further, many different electro-magnetic valveactuator arrangements may be provided besides the specific toggle rockerarmature arrangement disclosed. Electronic circuitry could be providedto independently actuate each valve element to open and close the inletand outlet valves in the metering unit. Moreover, in many applicationsof the metering apparatus, the drip chamber may be omitted from theapparatus, and the fluid chamber and associated interlock sensormechanism may be omitted. Furthermore, the fastening means for holdingthe metering unit and control unit together in fixed operativerelationship could be provided as part of the metering unit, if desired.

It will be observed that in accordance with the present invention, animproved apparatus is provided for controlling the dispensing of fluidthat is light in weight, easily portable and rugged in design. Themetering unit is the only portion of the apparatus which needs to bemaintained in a sterile condition, and the metering unit is provided asan inexpensive, disposable item that is replaced after each use of theapparatus. It will also be appreciated by those skilled in the art thatthe capabilities of the apparatus described fulfill the need for a safeintravenous administration device that is useful in a wide variety ofapplications for accurately controlling the rate of flow of fluid.

While the invention has been described with particular reference tospecific embodiments thereof in the interest of complete definiteness,it may be embodied in a large variety of forms diverse from the onesspecifically shown and described without departing from the scope andspirit of the invention as defined by the appended claims.

We claim:
 1. A disposable metering unit for use in controlling theintravenous administration of a fluid to a patient, comprising:inletconduit means for delivering fluid at a hydrostatic pressure from asource of fluid; metering means for receiving a predetermined incrementof fluid from the conduit means and for emptying the predeterminedincrement of fluid by the suction of gravity flow without addingsubstantial pressure to the hydrostatic pressure, said metering meansdefining a metering chamber having opposed inner walls, and movablediaphragm means positioned in the metering chamber, said diaphragm meansbeing capable of being moved at the hydrostatic pressure between a firstposition in which said diaphragm means is positioned against one of theopposed inner walls of the metering chamber with substantially all ofthe volume of the chamber being on one side of the diaphragm means, anda second position in which the diaphragm is in contact with the other ofsaid opposed inner walls of the metering chamber with substantially allof the volume of said metering chamber being on the other side of saiddiaphragm means, whereby said metering means may be repeatedly filledwith fluid to impel the diaphragm means into its second position andthen to drain said fluid from the metering means with the diaphragmmeans moving to the first position, whereby said predeterminedincrements of fluid may be of constant volume and may be passed throughsaid metering means; and outlet conduit means communicating with themetering means for receiving said increments wherein gravity suctionflow takes place to empty the metering means when the outlet means isopened, both said inlet and outlet conduit means communicating with themetering chamber at the same side of said diaphragm means, said meteringmeans defining exterior vent means communicating into said meteringchamber adjacent the opposed inner wall of said metering chamber withwhich the diaphragm is in contact in its second position, to facilitatefree flow of air into and out of said metering chamber as said diaphragmmeans moves between its first and second positions; and means forpermitting the alternative and sequential valving of fluid through saidinlet conduit means and outlet conduit means.
 2. The disposable meteringunit of claim 1 in which a projection is positioned on the inner wall ofeach inlet and outlet conduit means in opposed relation to apertures insaid walls to serve as part of said valve means.
 3. The metering unit ofclaim 1 in which the unit includes a rigid body portion and a coverportion with a cavity formed in the unit to provide the meteringchamber, the size of the cavity determining the capacity for thepredetermined increments of fluid.
 4. The metering unit of claim 1 inwhich the movable diaphragm means is resilient to conform to the shapeof the cavity.
 5. The metering unit of claim 1 in which the unitincludes a rigid body portion and a cover portion with an arcuate-shapedcavity formed in the body portion and a communicating arcuate-shapedcavity formed in the cover portion to provide the metering chamber. 6.The metering unit of claim 5 in which said diaphragm has anarcuate-shaped portion which conforms to the arcuate-shaped cavity ofone of the body and cover portions.
 7. The metering unit of claim 1 inwhich the metering chamber has a volumetric capacity of less than onecubic centimeter.
 8. The metering unit of claim 7 in which the valvemeans is actuated to provide the predetermined rate of administration offluid in the range of two tenths milliliter per minute to tenmilliliters per minute.
 9. The metering unit of claim 1 furtherincluding hydraulic means with a fluid chamber receiving fluid from themetering chamber for having fluid in the fluid chamber moved into themetering chamber to cause air in the metering chamber to be expelledthrough the inlet conduit means when the metering unit is in operativerelationship.
 10. The metering unit of claim 1 further including areservoir chamber adapted to receive a portion of the increments offluid from the source at a first hydrostatic pressure and to hold thefluid at a second hydrostatic pressure, the metering chamber receivingthe predetermined increment of fluid from the reservoir chamber andemptying the predetermined increment of fluid without adding substantialpressure to the second hydrostatic pressure.
 11. The metering unit ofclaim 10 in which means is provided for supporting the reservoir chamberwith respect to the metering chamber so that when the source of fluidhas been drained below a predetermined level, the second hydrostaticpressure of the fluid in the reservoir chamber is only sufficient tohave the metering chamber receive a portion of a predetermined incrementof fluid from the reservoir chamber to be emptied from the meteringchamber.
 12. A disposable metering unit for use in controlling theintravenous administration of a fluid to a patient, comprising:inletconduit means for delivering fluid at a hydrostatic pressure from asource of fluid; metering means for receiving a predetermined incrementof fluid from the conduit means and for emptying the predeterminedincrement of fluid by the suction of gravity flow without addingsubstantial pressure to the hydrostatic pressure, said metering meansdefining a metering chamber having opposed inner walls, and movablediaphragm means positioned in the metering chamber, said diaphragm meansbeing capable of being moved at said hydrostatic pressure between afirst position in which said diaphragm means is positioned against oneof the opposed inner walls of the metering chamber with substantiallyall of the volume of the chamber being on one side of the diaphragmmeans, and a second position in which the diaphragm is in contact withthe other of said opposed inner walls of the metering chamber withsubstantially all of the volume of said metering chamber being on theother side of said diaphragm means, whereby said metering means may berepeatedly filled with fluid to impel the diaphragm means into itssecond position and then to drain said fluid from the metering meanswith the diaphragm means moving to the first position, whereby saidpredetermined increments of fluid may be of constant volume and may bepassed through said metering means; outlet conduit means communicatingwith the metering means for receiving said increments wherein gravitysuction flow takes place to empty the metering means when the outletmeans is opened, the transverse dimensions of said inlet and outletconduit means being substantially less than the transverse dimension ofsaid metering means, said diaphragm means defining extensions residingin said inlet and outlet conduit means; both said inlet and outletconduit means communicating with the metering chamber at the same sideof said diaphragm means, said metering means defining exterior ventmeans communicating into said metering chamber adjacent the opposedinner wall of said metering chamber with which the diaphragm is incontact in its second position, to facilitate free flow of air into andout of said metering chamber as said diaphragm means moves between itsfirst and second positions; and apertures positioned in said inletconduit means and outlet conduit means adapted to permit passage ofplunger means respectively into said inlet and outlet conduit means torespectively press said diaphgram extensions into sealing relationshipwith walls of the inlet and outlet conduit means, to selectively blockliquid flow through said inlet and outlet conduit means.
 13. Thedisposable metering unit of claim 12 in which a projection is positionedon the inner wall of each inlet and outlet conduit means in opposedrelation to said apertures, to define a valve face against which saiddiaphragm extensions are pressed by said plunger means.
 14. A disposablemetering unit for use in controlling the intravenous administration offluid to a patient, comprising:(a) a reservoir chamber adapted toreceive a portion of the increments of fluid from a source of fluid at afirst hydrostatic pressure, and to hold the fluid at a secondhydrostatic pressure; (b) a metering chamber for receiving apredetermined increment of fluid from said reservoir chamber and foremptying the predetermined increment of fluid without adding substantialpressure to the second hydrostatic pressure, said metering chamberhaving a movable diaphragm means therein to meter a predeterminedquantity of fluid therethrough; (c) conduit means for delivering fluidat the source of fluid having a supply of predetermined increments offluid to the metering chamber; and (d) valve means actuatable forregulating the receiving and emptying of each of the predeterminedincrements of fluid by the metering chamber to be administered to thepatient at a predetermined rate of administration.
 15. The metering unitof claim 14 in which means is provided for supporting the reservoirchamber with respect to the metering chamber so that when the source offluid has been drained below a predetermined level, the secondhydrostatic pressure of the fluid in the reservoir chamber is onlysufficient to have the metering chamber receive a portion of apredetermined increment of fluid from the reservoir chamber to beemptied from the metering chamber.
 16. Apparatus for controlling theintravenous administration of fluid to a patient which comprises:inletconduit means for delivering fluid at a hydrostatic pressure from asource of fluid; metering means for receiving a predetermined incrementof fluid from the conduit means and for emptying the predeterminedincrement of fluid by the suction of gravity flow without addingsubstantial pressure to the hydrostatic pressure, said metering meansdefining a metering chamber having opposed inner walls, and movablediaphragm means positioned in the metering chamber, said diaphragm meanscapable of being moved at the hydrostatic pressure between a firstposition in which said diaphragm means is positioned against one of theopposed inner walls of the metering chamber with substantially all ofthe volume of the chamber being on one side of the diaphragm and asecond position in which the diaphragm is in contact with the other ofsaid opposed inner walls of the metering chamber with substantially allof the volume of said metering chamber being on the other side of saiddiaphragm means, whereby said metering chamber may be repeatedly filledwith fluid to impel the diaphragm means into its second position andthen to drain said fluid from the metering means with the diaphragmmeans moving to the first position, whereby said predeterminedincrements of fluid may be of constant volume and may be passed throughsaid metering means, both said inlet and outlet conduit meanscommunicating with the metering chamber at the same side of saiddiaphragm means, said metering means defining exterior vent meanscommunicating into said metering chamber adjacent the opposed inner wallof said metering chamber with which the diaphragm is in contact in itssecond position, to facilitate free flow of air into and out of saidmetering chamber as said diaphragm means moves between its first andsecond positions; and outlet conduit means communicating with themetering means for receiving said increments and conveying them to apatient wherein gravity suction flow takes place to empty the meteringmeans when the outlet means is opened, and valve means in said inlet andoutlet conduit means for the alternative and sequential valving of fluidthrough said inlet conduit means and outlet conduit means.
 17. Theapparatus of claim 16 in which the transverse dimensions of said inletand outlet conduit means are substantially less than the transversedimension of said metering means, said diaphragm means definingextensions residing in said inlet and outlet conduit means, aperturespositioned in said inlet conduit means and outlet conduit means, andplunger means adapted to pass respectively into said inlet and outletconduit means through said apertures to respectively press saiddiaphragm extensions into sealing relationship with walls of the inletand outlet conduit means, to selectively block liquid flow through saidinlet and outlet conduit means.
 18. The apparatus of claim 17 in which aprojection is positioned on the inner wall of each inlet and outletconduit means in opposed relationship to said apertures, to define avalve face against which said diaphragm extensions are pressed by saidplunger means.